Buffering.

For our sins we are listening to Christmas radio in the shop via the net.
Then it disappears due to buffering. The really crap station is obviously ok.
So whose fault is buffering? Bt or the people supplying the radio station?

Could be a dozen things. What's your internet connection like generally? Are there other devices using the connection? Can you lower the stream quality? Is your PC busy? Have you rebooted the router in the last five years? Do other videos / audio stream ok? Is there another PC / phone you can try? Does it use Flash, if so are you on the latest version?

Its the only thing running on the iPad. Internet is normally fine.
I'm assuming the router is the by box that sends the WiFi. Never rebooted it ,didn't know you needed to do stuff with it.
Imagine you were explaining stuff to a very bouncy spaniel and you are close to my level.

3G really shouldn't be faster, but it's possible. It's also possible that it's dropping to lower bitrate because it's on a mobile connection.

Are you trying the same station in both cases?

Have you tried using the iPad when it's right next to your wireless router? Streaming audio and video is particularly sensitive to a borderline wireless connection.

It's also possible that there's a network problem between BT and the source of radio station. Just because you get 19Mbps to a speed test site, doesn't mean that you can get 19Mbps to everywhere else on the internet.

"Buffering" is just the process of loading up the next few seconds of audio so that the music can carry on playing through minor network interruptions. If the data is arriving at your ipad slower than it's being played then the music has to stop whilst it refills the buffer.